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Happy feat Today's penguin species, from the massive emperor penguin through to the tiny blue penguin, all originated from an ancestor that lived just 20 million years ago, suggests a new study.

And researchers suspect a major climatic event in Antarctica 12 million years ago, may have been the major driving force behind the diversity of penguins that exist today.

Previous studies based on DNA and fossil records have given widely differing times for the origin of today's penguins.

DNA evidence suggests the most recent common ancestor of the group could have lived as long as 40.5 million years ago.

But, Dr Sankar Subramanian, an evolutionary biologist at Brisbane's Griffith University, says he and colleagues have now confirmed a previous DNA analysis that halves this timing.

"Our previous analysis revealed a different kind of timing which was more recent. So we wanted to do [a study] on a large scale," says Subramanian, lead author of the study published today in the Royal Society journal Biology Letters.

Subramanian, along with Dr David Lambert and colleagues in New Zealand and India, analysed samples from 11 of the 18 known species of penguin.

Using DNA sequencing, along with age estimates of multiple penguin fossils, the researchers "calibrated" a molecular clock to wind back time and pinpoint when penguins shared a common ancestor. Their result was 20.4 million years.

"In a way it's surprising for molecular data, but fossil-based studies did say it's around 15 to 20 million years ago," says Subramanian.

Climatic-driven burst

The greatest diversification of penguins, which resulted in the species we know of today, appears to have occurred 11 to 16 million years ago.

"Interestingly, around 12 million years ago Antarctica experienced a sharp decline in temperatures that resulted in a permanent ice cover over the continent," say the researchers.

Subramanian adds: "In evolutionary biology there are many examples when there is a drastic change in climate, many species are created in a burst in a short space of time."

Today, the range of penguins extends from the frozen Antarctic, through to Australia, New Zealand, and as far north as the Galapagos Islands.

Subramanian and colleagues plan to compare the differences that exist between penguin species to better understand how they have evolved.

"If you assume the ancestor lived in Antarctica it would have had characteristics to withstand harsh cold environments," he says.

"Now there are species living in Galapagos. The physiology, morphology and genome must have undergone significant changes to withstand such different climates."